package technology.ts;

import java.io.IOException;

public class Demot {
    public static void main(String[] args) {
        String name; String newName = "Nick"; newName = "Jason"; name = "Frieda";
        String newestName = name;
        name = null; // 关键点
    }

    public Number test11() throws Exception{
        int a= 0;
        return null;
    }

     public Number test() throws RuntimeException{
        int a= 0;
        return null;
    }

    public Number test22() throws IOException{
        int a= 0;
        return null;
    }



}

 class D2 extends Demot{

}
